Structural component consisting of a belt buckle, attachment hardware and force limiter

ABSTRACT

An assembly unit comprising a belt buckle ( 10 ) for the insert tongue of a vehicular seat belt, a fastener fitting ( 12 ) for the belt buckle ( 10 ) and a force limiter between the belt buckle ( 10 ) and the fastener fitting ( 12 ) is characterized in that the force limiter contains a traction means ( 14, 16 ) fixedly connected to the belt buckle ( 10 ), movable relative to the fastener fitting ( 12 ) by a predetermined travel, and a stretchable member ( 24 ) coupled to the belt buckle ( 10 ) and the fastener fitting ( 12 ), which can be stretched by a predetermined tensile force between the belt buckle ( 10 ) and the fastener fitting ( 12 ) being exceeded.

The invention relates to an assembly unit comprising a belt. buckle forthe insert tongue of a vehicular seat belt, a fastener fitting for thebelt buckle and a force limiter between the belt buckle and the fastenerfitting.

One such assembly unit is known from the German laid-open publication 3723 772. In this known assembly unit, the force limiter is formed by astretchable member which is configured integrally with the fastenerfitting serving to secure the belt buckle to the vehicle and which isprovided with a retaining lug for the belt buckle at its end facing awayfrom the fastener fitting. The stretchable member consists of severalannular stretch links integrally connected to each other, which arestretched once a predetermined tensile load between the belt buckle andthe fastener fitting is exceeded. The resulting increase in lengthbetween the fastener fitting and the belt buckle limits the maximumforce acting in the vehicular seat belt. Arranged in the interior of theannular stretch links are protruding limiting elements which, beyond apredetermined extension, come into contact with each other thus limitingany further increase in length of the stretchable member.

The drawback of this known assembly unit is that the characteristic ofincrease in length versus effective tensile force cannot be adjustedindependently of the maximum tensile load required to be transmitted bythe assembly unit.

The invention provides an assembly unit comprising a belt buckle, afastener fitting and a force limiter in which the characteristic of theincrease in length relative to the effective tensile force can bearbitrarily adapted to the respective requirements without influencingthe maximum permissible tensile load transmittable between the beltbuckle and the fastener fitting. In accordance with the invention,provision is made in an assembly unit of the aforementioned kind thatthe force limiter contains a traction means fixedly connected to thebelt buckle and movable relative to the fastener fitting by apredetermined travel, and a stretchable member coupled to the beltbuckle and the fastener fitting which member can be stretched by apredetermined tensile force between the belt buckle and the fastenerfitting being exceeded. Unlike prior art designs, the invention thusprovides in addition to the stretchable member a separate traction meansserving to transmit, at least in the fully stretched condition of theforce limiter, a substantial part of the tensile forces acting betweenthe belt buckle and the fastener fitting. Accordingly, the stretchablemember can thus be dimensioned irrespective of the required maximum loadcapacity of the assembly unit.

Preferably, it is provided for that the traction means consist of atleast one wire cable fixedly connected to the belt buckle and shiftablyguided at the fastener fitting, and that attached to the end of the wirecable facing away from the belt buckle is a stopper which following ashift in position of the wire cable relative to the fastener fitting bya predetermined travel, comes into contact with the fastener fitting.Since a wire cable is particularly well suitable for transmittingtensile loads and, in addition to this, can be put to usecost-effectively, an assembly unit can be achieved by this configurationat comparatively little expense with which, irrespective of the existingstretchable member, particularly high loads can be transmitted betweenthe belt buckle and the fastener fitting.

In accordance with a preferred embodiment of the invention it isprovided for that two wire cables are used which are anchored to theframe of the belt buckle and that the end of the stretchable memberfacing the belt buckle is fixedly crimped to the wire cables. By makinguse of two wire cables the belt buckle can be positioned reliably in thedesired orientation in the vehicle interior without necessitatingadditional expedients. Manufacturing the assembly unit in thisconfiguration involves minimum expense since the wire cables merely needto be inserted in the guide of the fastener fitting and then simplyrequiring the end of the stretchable member facing the belt buckle to befixedly crimped to the wire cables.

Advantageous aspects of the invention read from the sub-claims.

The invention will now be detailed with reference to various embodimentsillustrated in the attached drawings in which:

FIG. 1 is a front view in perspective of a first embodiment of theassembly unit in accordance with the invention;

FIG. 2 is a rear view in perspective of a second embodiment of theassembly unit in accordance with the invention;

FIG. 3 is a side view of a detail of the assembly unit as shown in FIG.2; and

FIG. 4 is a side view of a detail of a third embodiment of the assemblyunit.

Referring now to FIG. 1 there is illustrated schematically an assemblyunit in accordance with a first embodiment of the invention. Theassembly unit contains a belt buckle 10 into which an insert tongue of avehicular seat belt system can be inserted and which is coupled to afastener fitting 12 serving to secure the assembly unit to a vehicle(not shown). The belt buckle 10 contains in its interior a load-bearingframe (not shown) into which the loads of the seat belt are transmittedwith the insert tongue inserted. Fixedly connected to the load-bearingframe are two wire cables 14, 16 onto the end of which a stopper 18 ispressed.

The fastener fitting 12 is provided with two guide lugs 20, 22 claspingthe wire cables 14, 16. Following the end of the fastener fitting 12provided with the guide lugs 20, 22 is a stretchable member 24. Thelatter comprises two annular stretch links 26, 28 integrally connectedto each other between which, when desired, a predetermined breakingpoint 30 may be provided. Following the stretch link 28 are two arresterlugs 32, 34 fixedly crimped to the wire cables 14, 16. The two arresterlugs 32, 34 are configured and crimped to the wire cables 14, 16 suchthat they are able to transmit a maximum tensile force from the wirecables to the stretch links 26, 28 which is greater than the forceneeded to stretch the stretch links. Contrary to this, the lugs 20, 22serving to guide the wire cables 14, 16 at the fastener fitting 12 aremerely bent as far as is needed-to come into contact with the wirecables 14, 16 when lightly pretensioned; i.e. unlike the arrester lugs32, 34 the lugs 20, 22 do not provide for securing the wire cables 14,16 to the fastener fitting 12, they instead merely provide for apredetermined frictional force upon a relative movement between the wirecables 14, 16 and the fastener fitting 12.

Optionally a damping sleeve 36 may be arranged at the end of the wirecables 14, 16 adjacent the stopper 18.

When a tensile load is effective between the belt buckle 10 and thefastener fitting 12, three different phases can be observed. In a firstphase in which the tensile force is less than a first critical force, noincrease in length of the assembly unit occurs. The first critical forceis composed of the force needed to stretch the stretch links 26, 28 andthe force needed to overcome the friction between the lugs 20, 22 andthe wire cables 14, 16.

In a second phase in which the first critical force is exceeded, thestretch links 26, 28 are stretched since they are entrained by the wirecables 14, 16 via the lugs 32, 34, the wire cables 14, 16 being pulledthrough the lugs 20, 22. After a predetermined increase in length eitherthe optionally provided damping sleeve 36 or the stopper 18 comes intocontact with the lugs 20, 22 so that the increase in length is limited.The tensile force achieved at this point in time represents a secondcritical force.

In a third phase after the second critical force has been exceeded, thestretch links 26, 28 are stretched and either the damping sleeve 36 orthe stopper 18 is in contact with the lugs 20, 22. Any further increasein the tensile load results in no further increase in length.

The characteristic of increase in length versus effective tensile forcecan be set to practically any desired degree by designing the stretchlinks 26, 28 and the pretension of the lugs 20, 22 without thisinfluencing the maximum transmittable tensile force between the beltbuckle 10 and the fastener fitting 12.

Referring now to FIGS. 2 and 3 there is illustrated schematically asecond embodiment of the invention. This embodiment differs from thefirst embodiment by it employing three stretch links 26, 28, 29 insteadof two stretch links as well as by the arrangement of the tractioncables 14, 16 in the region of the fastener fitting 12. The tractioncables 14, 16 are deflected through 180° at the fastener fitting 12 sothat the stopper 18 is again oriented in the direction of the beltbuckle. Due to the deflection any shift in position of the wire cables14, 16 relative to the fastener fitting 12 is opposed by a resistingforce composed, for one thing, of the wrap friction in the region of thefastener fitting 12 and, for another, of the flexural rigidity of thewire cables 14, 16. In this embodiment the damping sleeve 36 is alreadyin contact with both the stopper 18 and the fastener fitting 12 in theresting position; i.e. it damping the relative movement between the wirecables 14, 16 and the fastener fitting 12 right from the start.

Referring now to FIG. 4 there is illustrated a detail of a thirdembodiment. Apart from the damping sleeve being missing, this thirdembodiment differs from the second embodiment in that the wire cables14, 16 protrude beyond the stopper 18. Provided at the fastener fitting12 are two lugs 38 which clasp the wire cables 14, 16 in the same way asthe lugs 20, 22. Depending on how the lugs 38 are designed and thedegree to which they are crimped to the wire cables 14, 16 they serveeither merely to guide the deflected section of the wire cables or, inaddition thereto, to provide a predetermined frictional force opposingany relative displacement between the wire cables 14, 16 and thefastener fitting 12.

What is claimed is:
 1. An assembly unit comprising a belt buckle (10)for the insert tongue of a vehicular seat belt, a fastener fitting (12)for said belt buckle (10) and a force limiter between said belt buckle(10) and said fastener fitting (12), said force limiter containing atraction means (14, 16) fixedly connected to said belt buckle (10),movable relative to said fastener fitting (12) by a predeterminedtravel, and a stretchable member (24) coupled to said belt buckle (10)and said fastener fitting (12), which can be stretched by apredetermined tensile force between said belt buckle (10) and saidfastener fitting (12) being exceeded, said traction means consisting ofat least one wire cable (14, 16) fixedly connected to said belt buckle(10) and shiftably guided at said fastener fitting (12), and a stopperbeing attached to the end of said wire cable (14, 16) which stopper (18)contacting said fastener fitting (12) following a shift in position ofsaid wire cable (14, 16) relative to said fastener fitting (12) by apredetermined travel said end of said wire cable (14, 16) protrudingfrom said stopper (18) and being guided by two lugs (38) formed on saidfastener fitting (12).
 2. Apparatus comprising: a vehicle seat beltbuckle (10); and a fastener fitting (12) for said vehicle seat beltbuckle (10); and a force limiter having a traction means (14, 16)connected to said vehicle seat belt buckle (10) and extending betweensaid seat belt buckle (10) and said fastener fitting (12), and astretchable member (24) having a predetermined tensile strength arrangedin parallel to said traction means (14,16) and being coupled to saidtraction means (14,16) and said fastener fitting (12), said stretchablemember (24) stretching in length when said predetermined tensilestrength is exceeded, said traction means comprising at least one wirecable (14, 16) fixedly connected to said belt buckle (10) and shiftablyguided at said fastener fitting (12), and a stopper (18) attached to theend of said wire cable (14, 16), said stopper, following a shift inposition of said wire cable (14, 16) relative to said fastener fitting(12) by a predetermined travel, coming into contact with said fastenerfitting (12), and at least two lugs (20, 22) against which said stopper(18) can come into contact guiding said wire cable (14, 16) at saidfastener fitting (12).
 3. The apparatus of claim 2 wherein said lugs(20, 22, 38) are pretensioned relative to said wire cable (14, 16). 4.Apparatus comprising: a vehicle seat belt buckle (10); and a fastenerfitting (12) for said vehicle seat belt buckle (10); and a force limiterhaving a traction means (14, 16) connected to said vehicle seat beltbuckle (10) and extending between said seat belt buckle (10) and saidfastener fitting (12), and a stretchable member (24) having apredetermined tensile strength arranged in parallel to said tractionmeans (14,16) and being coupled to said traction means (14,16) and saidfastener fitting (12), said stretchable member (24) stretching in lengthwhen said predetermined tensile strength is exceeded, said tractionmeans comprising at least one wire cable (14, 16) fixedly connected tosaid belt buckle (10) and shiftably guided at said fastener fitting(12), and a stopper (18) attached to the end of said wire cable (14,16), said stopper, following a shift in position of said wire cable (14,16) relative to said fastener fitting (12) by a predetermined travel,coming into contact with said fastener fitting (12), said wire cable(14, 16) being deflected through about 180° in the region of saidfastener fitting (12) and said stopper (18) coming into contact withsaid fastener fitting (12) at the point of deflection.
 5. Apparatuscomprising: a vehicle seat belt buckle (10); and a fastener fitting (12)for said vehicle seat belt buckle (10); and a force limiter having atraction means (14, 16) connected to said vehicle seat belt buckle (10)and extending between said seat belt buckle (10) and said fastenerfitting (12), and a stretchable member (24) having a predeterminedtensile strength arranged in parallel to said traction means (14,16) andbeing coupled to said traction means (14,16) and said fastener fitting(12), said stretchable member (24) stretching in length when saidpredetermined tensile strength is exceeded, said traction meanscomprising at least one wire cable (14, 16) fixedly connected to saidbelt buckle (10) and shiftably guided at said fastener fitting (12), anda stopper (18) attached to the end of said wire cable (14, 16), saidstopper, following a shift in position of said wire cable (14, 16)relative to said fastener fitting (12) by a predetermined travel, cominginto contact with said fastener fitting (12), and a damping sleeve (36)arranged on said wire cable (14, 16) between said fastener fitting (12)and said stopper (18).
 6. Apparatus comprising: a vehicle seat beltbuckle (10); and a fastener fitting (12) for said vehicle seat beltbuckle (10); and a force limiter having a traction means (14, 16)connected to said vehicle seat belt buckle (10) and extending betweensaid seat belt buckle (10) and said fastener fitting (12), and astretchable member (24) having a predetermined tensile strength arrangedin parallel to said traction means (14,16) and being coupled to saidtraction means (14,16) and said fastener fitting (12), said stretchablemember (24) stretching in length when said predetermined tensilestrength is exceeded, said traction means comprising at least one wirecable (14, 16) fixedly connected to said belt buckle (10) and shiftablyguided at said fastener fitting (12), and a stopper (18) attached to theend of said wire cable (14, 16), said stopper, following a shift inposition of said wire cable (14, 16) relative to said fastener fitting(12) by a predetermined travel, coming into contact with said fastenerfitting (12), said two wire cables (14, 15) being anchored to the frameof said belt buckle (10) and an end (32, 34) of said stretchable member(24) being fixedly crimped to said wire cable (14, 16).